5 ms·

No, enough with this nonsense. Capturing, liquefying and transforming CO2 into fuel requires energy - due to thermodynamic limits, much more energy than what th

by yholio 5y ago

No, enough with this nonsense. Capturing, liquefying and transforming CO2 into fuel requires energy - due to thermodynamic limits, much more energy than what the fuel can give back. You then take that fuel, and... burn it into 25% efficient engines that spew the very same CO2 back into the air, along with some new carcinogenic fumes and acid-rain inducing nitrogen oxides? No, just no, full stop. They way forward is electrification of everything, using only carbon-neutral energy, renewables &nuclear. No hydrogen, no methane, no electric to fuel, let's not do these physical stupidities to keep dying industries alive.

realusername 5y ago
Thermodynamics is about energy not CO2, you can design negative CO2 devices and we even have proof in nature of that since that's what trees are doing.
- wyager 5y ago
  There are several conceptual issues here, but one of them is that trees require energy from sunlight to turn CO2 into other things.
  - realusername 5y ago
    Yes but we don't have an energy problem, we have a CO2 problem and there's no law of physics preventing to absorb more CO2 than you emit.
    - diarrhea 5y ago
      That's true but assumes the captured CO2 remains that, captured. The article revolves around the idea of turning CO2 into fuel. Fuel which is burned, releasing that same CO2 again while having wasted a lot of intermediate energy. At best, that energy was renewable and would've been curtailed otherwise (hence wasted). Then you didn't "use energy" but it was still an utterly useless exercise. Now, if the carbon remains captured and the energy for capturing is renewable, we are in business. I'm not aware that is done on a meaningful scale yet though.
- peteradio 5y ago
  But thats not what this is. Fuel is intended to be consumed, seems like this is at best carbon neutral assuming totally neutral power source. Are our current power sources on average neutral or are they much more carbon positive?
  - realusername 5y ago
    > But thats not what this is. Fuel is intended to be consumed, seems like this is at best carbon neutral assuming totally neutral power source Indeed, that's their goal, the issue is that currently we emit a lot so even making the fuel close to neutral (minus production inefficiencies) is already a huge progress. Going negative isn't for tomorrow unfortunately.
- marginalia_nu 5y ago
  The problem is that this requires reversing entropy. Turning CO2 into something that can burn into CO2 requires more energy than you get back while burning it, even in an optimal engine. This is true if humans reverse entropy or if trees do it.
  - realusername 5y ago
    Economics are a different story yeah, there's no way to make carbone absorption economically possible without some carbon scheme designed by the country. They won't happen on their own that's for sure, that's where legislation should come in place.
  - DennisP 5y ago
    It's not an energy source, it's a battery.
colordrops 5y ago
Agreed that the future is electrification, but it will take trillions of dollars and a lot of time to replace all internal combustion engines. What should we do in the meantime? It seems that using renewable energy to make carbon neutral fuels for these vehicles makes a lot of sense. What is "nonsense" about this?
- mrguyorama 5y ago
  It would take more time, energy, money, and resources to build out enough solar and wind (etc) to turn enough CO2 into enough fuel for all our cars than it takes to just replace the cars with electric ones and use that massive solar and wind grid to just power them straight
  - colordrops 5y ago
    It's not all or nothing, and further more the electricity from solar and wind is fungible and can be used for either fuel generation or direct usage by electric cars, so it would serve us either way, no matter how long it took. These things are not contradictory. We can build out more renewable electricity supply, replace with electric cars, and generate carbon neutral fuel all at the same time. You are underestimating how long and difficult the ICE replacement is going to take. It's not like a single organization can just wave a wand and all gas cars would be replaced over night.
    - yholio 5y ago
      In Europe, fosil fuel engines are already 2-4 times more expensive to run than electrics. In 11 years, which is the average age of a car in Europe, the majority of private vehicles will switch naturally for purely economic reasons. In 20 years, the same will be true for busses, trucks & tractors. And it will be driven solely by better economics.
      - diarrhea 5y ago
        And what do you get by replacing one ICE vehicle in Europe with an electric one? You get two cars. A shiny new electric one running in (Central) Europe, and that same old stinky ICE one running in Eastern Europe, Asia or Africa. The poorer countries will enjoy an influx and thus price decrease of valuable cars and happily drive them for decades to come. The problem of course is that the planet doesn't care. Europe got cleaner but the planet got worse. Whereas Europe can outsource its dirty issues (waste, emissions, ...), the planet cannot. It stops there and we all lose. I think the vast introduction of and blind focus on e-mobility is a mistake. Other areas are much more significant sources for GHG (industry, heating, A/C).
it_citizen 5y ago
I get that blue hydrogen might be a controversial topic but isn't there at least a case to make for green hydrogen in some sectors that might be hard to electrify such as aviation? Or even as an alternative storage solution since the effort to scale up nuclear seems pretty much dead in the water. I know it is a long shot: it is not yet competitive, there are still very few electrolyzers but some part of the world such as Europe seems pretty committed to try to make it work.
btilly 5y ago
The title needs to be changed. Because this isn't about climate change, and the research, contents of the article, and current article title are clear on that. This is about space exploration. Literally it is about how to make fuel on Mars so that we can make the round trip without having to deliver fuel so we can make it back. And, sorry, but there is no way with current technology to launch significant payloads into space using electric.
_Microft 5y ago
It can make sort of sense for applications for which the energy density of the fuel (like for airplanes or rockets) matters a lot. The energy density of current generation lithium ion batteries is insufficient to allow for long-range flights. Synthetic fuels could allow planes to still travel around the world while being effectively net zero emitters because the CO_2 was harvested from the atmosphere (or another, unavoidable CO_2 source). The production of the fuel might be inefficient but at least it would work.
- yholio 5y ago
  There is already a good solution for planes: ammonia, manufactured efficiently from green hydrogen. You will never be able to use gaseous or liquid hydrogen on planes due to the high volume, weight and risk associated with known storage methods. Ammonia seems to strike the right balance: https://www.ammoniaenergy.org/articles/zero-emission-aircraft-ammonia-for-aviation/ https://www.ammoniaenergy.org/articles/zero-emission-aircraf...
  - _Microft 5y ago
    How are they planning to work around ammonia's toxicity problem? It's fatal if breathed in at concentrations like we currently have CO_2 in the atmosphere (> ~400ppm). If a tank with conventional jetfuel or methane springs a leak or has to be dumped, you've got a huge problem. If that happens with an ammonia tank, you are most likely toast either way.
    - ncmncm 5y ago
      Millions of tons of ammonia are produced every year. It is the favored refrigerant in industrial sites, such as warehouse-sized freezers. We have most of a century's experience handling ammonia in such quantities. But ammonia is probably a better choice for fueling trains and ships than for aircraft.
- ncmncm 5y ago
  Liquid hydrogen LH2 electrically synthesized on-site at airports from excess peak production will be important in aviation after maybe 2035 (provided civilization doesn't collapse first). Aside from LH2's usefully extreme energy density, pumping less CO2 directly into the stratosphere would be good. We may reasonably expect production of the needed aerogel-insulated LH2 tankage to be mature by then.
blacksmith_tb 5y ago
We'll just use that fuel to make plastic, and scatter it all over the surface of the planet. So it's really just a continuation of the ad hoc sequestration program already under way.
qw3rty01 5y ago
In the article, the idea was to store excess green electricity (from solar/wind farms for example) by capturing CO2 that is generated from fossil fuels. I do agree that claiming it will address climate change is a bit of a stretch, since that CO2 is still going back into the environment when the methane is used, but it does mean getting more energy per unit of CO2.
dang 5y ago
Please don't fulminate. That's in the site guidelines (https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html), because it tends to produce low-quality discussion which we're hoping to avoid here. I'm sure you can make your substantive points thoughtfully, so please do that instead.
eightysixfour 5y ago
I was with you until no hydrogen. While it is inefficient in compared to batteries, as long as it is being produced with carbon-neutral energy then there are areas where its kWh/kg ratio and comparatively rapid refilling are extremely beneficial.
- yholio 5y ago
  You should take that kWh/kg figure with a kg of salt. You need a heavy COPV tank to store hydrogen under pressure, a 100 kg tank might store only a few kg of fuel, take 400 liter to do so, and be comparable with a 30l conventional fuel tank: https://www.fsec.ucf.edu/en/consumer/hydrogen/basics/documents/task2_gaseous_h2.pdf https://www.fsec.ucf.edu/en/consumer/hydrogen/basics/documen...
  - eightysixfour 5y ago
    Sure, and using it for small vehicles seems like the worst place to use them. I'm thinking more about vehicles that need significantly more fuel - diesel electric trains, container ships, airplanes, etc. It won't work in all of those situations since hydrogen is so hard to manage, but there are a number of applications where batteries are not the right answer yet. Battery weight is going to scale close to linearly with capacity, hydrogen tank weight should not.
    - ncmncm 5y ago
      LH2 tanks on aircraft, insulated with aerogel, can be very light. But the extra volume will mean a need for new airframes. Trains and ships, and maybe trucks, will do better with ammonia. The tanks are bigger, but those have room, and existing engines can burn ammonia with just changes to plumbing.
deleted 5y ago
[deleted]
missedthecue 5y ago
You are correct that they can't break the laws of thermodynamics, but they don't need to in order to have a workable business model. The reason is because you don't need it to result in more energy than you put in. You just need it to result in more revenue than input costs. This is practically possible because different energy forms have different costs and they're not all substitutable for each other. For instance, electricity may become a lot cheaper than liquid fuel, but you can't electrify a long range airliner, or most military equipment. So in a world where a watt of electricity can be bought for 1/3 the price of a watt of kerosene, using 2 units of electricity energy to make 1 unit of liquid fuel energy would be economical. (made up numbers, you get the point)

by yholio 5y ago

realusername 5y ago

Thermodynamics is about energy not CO2, you can design negative CO2 devices and we even have proof in nature of that since that's what trees are doing.

wyager 5y ago
There are several conceptual issues here, but one of them is that trees require energy from sunlight to turn CO2 into other things.
- realusername 5y ago
  Yes but we don't have an energy problem, we have a CO2 problem and there's no law of physics preventing to absorb more CO2 than you emit.
  - diarrhea 5y ago
    That's true but assumes the captured CO2 remains that, captured. The article revolves around the idea of turning CO2 into fuel. Fuel which is burned, releasing that same CO2 again while having wasted a lot of intermediate energy. At best, that energy was renewable and would've been curtailed otherwise (hence wasted). Then you didn't "use energy" but it was still an utterly useless exercise. Now, if the carbon remains captured and the energy for capturing is renewable, we are in business. I'm not aware that is done on a meaningful scale yet though.
peteradio 5y ago
But thats not what this is. Fuel is intended to be consumed, seems like this is at best carbon neutral assuming totally neutral power source. Are our current power sources on average neutral or are they much more carbon positive?
- realusername 5y ago
  > But thats not what this is. Fuel is intended to be consumed, seems like this is at best carbon neutral assuming totally neutral power source Indeed, that's their goal, the issue is that currently we emit a lot so even making the fuel close to neutral (minus production inefficiencies) is already a huge progress. Going negative isn't for tomorrow unfortunately.
marginalia_nu 5y ago
The problem is that this requires reversing entropy. Turning CO2 into something that can burn into CO2 requires more energy than you get back while burning it, even in an optimal engine. This is true if humans reverse entropy or if trees do it.
- realusername 5y ago
  Economics are a different story yeah, there's no way to make carbone absorption economically possible without some carbon scheme designed by the country. They won't happen on their own that's for sure, that's where legislation should come in place.
- DennisP 5y ago
  It's not an energy source, it's a battery.

colordrops 5y ago

Agreed that the future is electrification, but it will take trillions of dollars and a lot of time to replace all internal combustion engines. What should we do in the meantime? It seems that using renewable energy to make carbon neutral fuels for these vehicles makes a lot of sense. What is "nonsense" about this?

mrguyorama 5y ago
It would take more time, energy, money, and resources to build out enough solar and wind (etc) to turn enough CO2 into enough fuel for all our cars than it takes to just replace the cars with electric ones and use that massive solar and wind grid to just power them straight
- colordrops 5y ago
  It's not all or nothing, and further more the electricity from solar and wind is fungible and can be used for either fuel generation or direct usage by electric cars, so it would serve us either way, no matter how long it took. These things are not contradictory. We can build out more renewable electricity supply, replace with electric cars, and generate carbon neutral fuel all at the same time. You are underestimating how long and difficult the ICE replacement is going to take. It's not like a single organization can just wave a wand and all gas cars would be replaced over night.
  - yholio 5y ago
    In Europe, fosil fuel engines are already 2-4 times more expensive to run than electrics. In 11 years, which is the average age of a car in Europe, the majority of private vehicles will switch naturally for purely economic reasons. In 20 years, the same will be true for busses, trucks & tractors. And it will be driven solely by better economics.
    - diarrhea 5y ago
      And what do you get by replacing one ICE vehicle in Europe with an electric one? You get two cars. A shiny new electric one running in (Central) Europe, and that same old stinky ICE one running in Eastern Europe, Asia or Africa. The poorer countries will enjoy an influx and thus price decrease of valuable cars and happily drive them for decades to come. The problem of course is that the planet doesn't care. Europe got cleaner but the planet got worse. Whereas Europe can outsource its dirty issues (waste, emissions, ...), the planet cannot. It stops there and we all lose. I think the vast introduction of and blind focus on e-mobility is a mistake. Other areas are much more significant sources for GHG (industry, heating, A/C).

it_citizen 5y ago

I get that blue hydrogen might be a controversial topic but isn't there at least a case to make for green hydrogen in some sectors that might be hard to electrify such as aviation? Or even as an alternative storage solution since the effort to scale up nuclear seems pretty much dead in the water. I know it is a long shot: it is not yet competitive, there are still very few electrolyzers but some part of the world such as Europe seems pretty committed to try to make it work.

btilly 5y ago

The title needs to be changed. Because this isn't about climate change, and the research, contents of the article, and current article title are clear on that. This is about space exploration. Literally it is about how to make fuel on Mars so that we can make the round trip without having to deliver fuel so we can make it back. And, sorry, but there is no way with current technology to launch significant payloads into space using electric.

_Microft 5y ago

It can make sort of sense for applications for which the energy density of the fuel (like for airplanes or rockets) matters a lot. The energy density of current generation lithium ion batteries is insufficient to allow for long-range flights. Synthetic fuels could allow planes to still travel around the world while being effectively net zero emitters because the CO_2 was harvested from the atmosphere (or another, unavoidable CO_2 source). The production of the fuel might be inefficient but at least it would work.

yholio 5y ago
There is already a good solution for planes: ammonia, manufactured efficiently from green hydrogen. You will never be able to use gaseous or liquid hydrogen on planes due to the high volume, weight and risk associated with known storage methods. Ammonia seems to strike the right balance: https://www.ammoniaenergy.org/articles/zero-emission-aircraft-ammonia-for-aviation/ https://www.ammoniaenergy.org/articles/zero-emission-aircraf...
- _Microft 5y ago
  How are they planning to work around ammonia's toxicity problem? It's fatal if breathed in at concentrations like we currently have CO_2 in the atmosphere (> ~400ppm). If a tank with conventional jetfuel or methane springs a leak or has to be dumped, you've got a huge problem. If that happens with an ammonia tank, you are most likely toast either way.
  - ncmncm 5y ago
    Millions of tons of ammonia are produced every year. It is the favored refrigerant in industrial sites, such as warehouse-sized freezers. We have most of a century's experience handling ammonia in such quantities. But ammonia is probably a better choice for fueling trains and ships than for aircraft.
ncmncm 5y ago
Liquid hydrogen LH2 electrically synthesized on-site at airports from excess peak production will be important in aviation after maybe 2035 (provided civilization doesn't collapse first). Aside from LH2's usefully extreme energy density, pumping less CO2 directly into the stratosphere would be good. We may reasonably expect production of the needed aerogel-insulated LH2 tankage to be mature by then.

blacksmith_tb 5y ago

We'll just use that fuel to make plastic, and scatter it all over the surface of the planet. So it's really just a continuation of the ad hoc sequestration program already under way.

qw3rty01 5y ago

In the article, the idea was to store excess green electricity (from solar/wind farms for example) by capturing CO2 that is generated from fossil fuels. I do agree that claiming it will address climate change is a bit of a stretch, since that CO2 is still going back into the environment when the methane is used, but it does mean getting more energy per unit of CO2.

dang 5y ago

Please don't fulminate. That's in the site guidelines (https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html), because it tends to produce low-quality discussion which we're hoping to avoid here. I'm sure you can make your substantive points thoughtfully, so please do that instead.

eightysixfour 5y ago

I was with you until no hydrogen. While it is inefficient in compared to batteries, as long as it is being produced with carbon-neutral energy then there are areas where its kWh/kg ratio and comparatively rapid refilling are extremely beneficial.

yholio 5y ago
You should take that kWh/kg figure with a kg of salt. You need a heavy COPV tank to store hydrogen under pressure, a 100 kg tank might store only a few kg of fuel, take 400 liter to do so, and be comparable with a 30l conventional fuel tank: https://www.fsec.ucf.edu/en/consumer/hydrogen/basics/documents/task2_gaseous_h2.pdf https://www.fsec.ucf.edu/en/consumer/hydrogen/basics/documen...
- eightysixfour 5y ago
  Sure, and using it for small vehicles seems like the worst place to use them. I'm thinking more about vehicles that need significantly more fuel - diesel electric trains, container ships, airplanes, etc. It won't work in all of those situations since hydrogen is so hard to manage, but there are a number of applications where batteries are not the right answer yet. Battery weight is going to scale close to linearly with capacity, hydrogen tank weight should not.
  - ncmncm 5y ago
    LH2 tanks on aircraft, insulated with aerogel, can be very light. But the extra volume will mean a need for new airframes. Trains and ships, and maybe trucks, will do better with ammonia. The tanks are bigger, but those have room, and existing engines can burn ammonia with just changes to plumbing.

deleted 5y ago

[deleted]

missedthecue 5y ago

You are correct that they can't break the laws of thermodynamics, but they don't need to in order to have a workable business model. The reason is because you don't need it to result in more energy than you put in. You just need it to result in more revenue than input costs. This is practically possible because different energy forms have different costs and they're not all substitutable for each other. For instance, electricity may become a lot cheaper than liquid fuel, but you can't electrify a long range airliner, or most military equipment. So in a world where a watt of electricity can be bought for 1/3 the price of a watt of kerosene, using 2 units of electricity energy to make 1 unit of liquid fuel energy would be economical. (made up numbers, you get the point)